Preparation of tris(2-chlorovinyl) borane



Dec. 22, 1959 B. F. CLARK FETAL PREPARATION OF mxsmwmoaovmyu BORANE Filed Feb. 20. 1958 Benjamin F Clark m m im s p .mrmfl m H .m. m m QKW Wmm d EMP BY gwad a ggzw United States Patent 2,918,498 PREPARATION OF TRIS(2-CHLOROVINYL) BORANE Application February 20, 1958, Serial No. 716,513 1 Claim. (Cl. 260-6065) Edward Gipstein, N ew This invention relates to a method for the preparation of tris (2-chlorovinyl) borane from chlorobis (2-chl0rovinyl) borane.

Tris (2-chlorovinyl) borane is a useful chemical compound in that it can be hydrogenated to form triethyl borane as described in the application of Benjamin F. Clark et al., Serial No. 716,510, filed of even date herewith and entitled Manufacture. In accordance with the method of this invention, the desired tris (2-chlorovinyl) borane is prepared by heating chlorobis (Z-chlorovinyl) borane in liquid phase at a temperature within the range from 140 C. to 190 C. The operation is carried out in the absence of a catalyst and with the removal of dichloro (Z-chlorovinyl) borane from the reaction mixture. The reaction temperature should not be permitted to go above 190 C., or otherwise undesired side reactions take place. Beyond that point, the temperature of the reactor is such that the starting material chlorobis (2-chlorovinyl) borane begins to distill over, the distillation of dichloro (2-chlorovinyl) borane ceases and a side reaction occurs which liberates volatile materials, thus decreasing the ultimate yield of the desired product. The reaction which takes place when the present process is carried out can be represented by the following equation:

The following example illustrates but does not limit the practice of this invention.

Example The apparatus utilized is shown in the accompanying drawing. It consisted of a one-liter round-bottom distillation flask 1 equipped with a thermowell 2 to which there was attached a 17 inch Vigreau column 3. The top of the Vigreau column was equipped with a thermometer 4 and was also connected to an 8 inch Fried- Wallingford, and Perry R.

richs condenser 5 which was water cooled by means of Water introduced through inlet 6 and removed by means of outlet 7. Attached to the bottom of the Friedrichs condenser was a 250 cc. round-bottom flask 8 which served as a product receiver. There was also attached to the bottom of the Friedrichs condenser 21 line 9 for the introduction of nitrogen into the system. A mercury bubble-oil '10 was connected to the nitrogen inlet line and a connection 11 for attaching the reaction system to a vacuum system was also provided on the nitrogen inlet line.

Approximately 3.12 gram moles of chlorobis (2- chlorovinyl) borane was charged to the distillation flask and it was attached to the Vigreau column. The nitrogen inlet line was closed and the system was connected to the vacuum apparatus and evacuated to an absolute pressure of about 10 mm. of Hg in order to remove any oxygen present. Then, the vacuum in the system Was relieved with nitrogen, the vacuum system closed oft and finally the nitrogen inlet to the reaction system was closed. Next, the distillation flask and contents were heated to reflux temperature C.) and the heating was continued until the pot temperature reached a temperature of about 186 to 190 C. During the heating period, dichloro (2-chlorovinyl) borane passed overhead and into the water cooled condenser. The condensed dichloro (2-chlorovinyl) borane was collected in the product receiver. After the reflux operation had been com pleted, heating was stopped and the nitrogen inlet opened to the reaction system so that the material remaining in the one-liter flask was allowed to cool to room temperature under a nitrogen blanket.

This material was then distilled through a Vigreau column under reduced pressure to separate the chlorobis (Z-chlorovinyl) borane from the tris (2-chlorovinyl) borane present in the flask at the conclusion of the refluxing period. During this reduced pressure distillation, the first fraction which distilled over was the chlorobis (2-chlorovinyl) borane (1.18 gram moles) at a boiling point of 32 C. under an absolute pressure of 2 mm. of Hg and the second fraction removed was the tris (2-chlorovinyl) borane (0.179 gram mole) which distilled over at a temperature of 55 C. under an absolute pressure of 0.05 mm. of Hg.

It is claimed:

A method for the preparation of tris (2-chlorovinyl) borane which comprises heating chlorobis (2-chlorovinyl) borane in liquid phase at a temperature within the range from 140 C. to 190 C. in the absence of a catalyst while removing dichloro (Z-chlorovinyl) borane from the reaction mixture.

No references cited. 

